Maraviroc (UK-427,857), a selective and reversible CCR5 coreceptor antagonist, has been shown to be active in vitro against a wide range of clinical isolates (including those resistant to existing classes). In HIV-1 infected patients, maraviroc (UK-427,857) given as monotherapy for 10 days reduced HIV-1 viral load by up to 1.6 log, consistent with currently available agents. Safety and toleration have been studied in over 400 subjects for up to 28 days at 300 mg twice daily. No significant effects were seen on the QTc interval. The goal of this study is to compare the safety and efficacy of maraviroc (UK-427,857) versus efavirenz, when each are combined with two other antiretroviral agents, in patients who are previously naive to antiretroviral therapy. This study will involve approximately 200 centers from around the world to achieve a total randomized subject population of 1071 subjects. Patients will be randomly assigned to one of three groups: maraviroc (UK-427,857) 300 mg once daily added to zidovudine/lamivudine (300 mg/150 mg twice daily), Maraviroc (UK-427,857) 300 mg twice daily added to zidovudine/lamivudine (300 mg/150 mg twice daily) or efavirenz (600 mg once daily) added to zidovudine/lamivudine (300 mg/150 mg twice daily). The study will enroll over approximately an 18 month period (5 months Phase 2b run-in, 13 months Phase 3) with 96 weeks of treatment. This may be extended for an additional 3 years depending on the results at 96 weeks. Physical examinations will be performed at study entry, weeks 4, 8, 12, 16, 20, 24, 32, 40, 48, 60, 72, 84 and 96. Blood samples will also be taken at study entry, weeks 2, 4, 8, 12, 16, 20, 24, 32, 40, 48, 60, 72, 84 and 96. Additionally, blood samples will be drawn twice, at least 30 minutes apart, at weeks 2 and 48 for maraviroc (UK-427,857) pharmacokinetic analysis. As part of this clinical study a blood sample will be taken for non-anonymized pharmacogenetic analysis. Patients will undergo a 12-lead electrocardiogram at study entry, weeks 24, 48 and 96. A computerized tomography (CT) scan will also be performed, at selected centers, at study entry and week 96. Patients will be asked to complete a symptom distress questionnaire at study entry, weeks 12, 24, 48 and 96.

A Multicenter, Randomized, Double-Blind, Comparative Trial Of A Novel CCR5 Antagonist, UK-427,857, In Combination With Zidovudine/Lamivudine Versus Efavirenz In Combination With Zidovudine/Lamivudine For The Treatment Of Antiretroviral-Naive HIV-1 Infected Subjects

Percentage of Participants With Viral Load of Less Than 400 Copies/Milliliter [Copies/mL] and Less Than 50 Copies/mL of Human Immunodeficiency Virus (HIV)-1 Ribonucleic Acid (RNA) at Week 48 for Full Analysis Set (FAS) Population [ Time Frame: Week 48 ] [ Designated as safety issue: No ]

Percentage of Participants With Viral Load of Less Than 400 Copies/mL and Less Than 50 Copies/mL of HIV-1 RNA at Week 48 for Per Protocol (PP) Population [ Time Frame: Week 48 ] [ Designated as safety issue: No ]

Percentage of participants with viral load of less than 400 copies/mL and less than 50 copies/mL of HIV-1 RNA were not analyzed for participants originally randomized to maraviroc once daily arm since after termination, focus was shifted from efficacy and safety to only safety as reflected in the abbreviated set of efficacy measures noted in the amended planned analysis.

Secondary Outcome Measures:

Percentage of Participants With HIV-1 RNA Levels of Less Than 400 Copies/mL and Less Than 50 Copies/mL at Week 48 Analyzed Using Logistic Regression [ Time Frame: Week 48 ] [ Designated as safety issue: No ]

Percentage of Participants With HIV-1 RNA Levels of Less Than 400 Copies/mL and Less Than 50 Copies/mL at Week 96 Analyzed Using Logistic Regression [ Time Frame: Week 96 ] [ Designated as safety issue: No ]

TAD from baseline was calculated as area under the curve (AUC) of HIV-1 RNA load (log10 copies/mL) divided by time period minus baseline HIV-1 RNA load (log10 copies/mL). Baseline value calculated as average of pre-dose measurements collected at screening, randomization, and immediately pre-dose. Data not analyzed for participants originally randomized to maraviroc once daily arm since after termination, focus was shifted from efficacy and safety to only safety as reflected in the abbreviated set of efficacy measures noted in the amended planned analysis.

Baseline value calculated as the average of pre-dose measurements collected at screening and immediately pre-dose. Change from baseline in lymphocyte CD8 count at Week 48 and 96 was not analyzed for participants originally randomized to maraviroc once daily arm since after termination, focus was shifted from efficacy and safety to only safety as reflected in the abbreviated set of efficacy measures noted in the amended planned analysis.

Time to virologic failure based on observed HIV-1 RNA levels and failure events (death;permanent discontinuation of drug;lost to follow-up [LTFU];new anti-retroviral drug added [except background drug change to drug of same class];or on open label for early non-response or rebound). Failure:at Time 0 if level not <400 copies/mL(2 consecutive visits) before events or last available visit;at time of earliest event if level <400 copies/mL(2 consecutive visits);failure if level >=400 copies/mL(2 consecutive visits) or 1 visit >=400 copies/mL followed by permanent discontinuation of drug or LTFU.

Number of Participants Per Tropism Status at Baseline and at the Time of Treatment Failure Through Week 48 [ Time Frame: Baseline, time of failure through Week 48 ] [ Designated as safety issue: No ]

Number of participants per tropism status (C-X-C chemokine receptor 5 {CCR5} [R5], C-X-C chemokine receptor type 4 {CXCR4} [X4], Dual/mixed [DM], or Non-reportable/Non-phenotypable [NR/NP]) at baseline and time of treatment failure analyzed through week 48 visit. Treatment failure: discontinuation due to insufficient clinical response. Tropism result was censored for participants with viral load <500 copies/mL at time of treatment failure categorized as below lower limit of quantification (BLQ). The assessment for time of treatment failure was defined as last on treatment assessment.

Number of Participants Per Tropism Status at Baseline and at the Time of Treatment Failure Through Week 96 [ Time Frame: Baseline, time of failure through Week 96 ] [ Designated as safety issue: No ]

Number of participants per tropism status (R5, X4, DM, or NR/NP) at baseline and time of treatment failure analyzed through week 96 visit. Treatment failure defined as insufficient clinical response. Tropism result was censored for participants with viral load <500 copies/mL at time of treatment failure categorized as BLQ. The assessment for time of treatment failure was defined as last on treatment assessment.

Number of Participants With Phenotypic Resistance at Time of Treatment Failure Through Week 48 and 96 [ Time Frame: Screening, time of failure through Week 48, Week 96 ] [ Designated as safety issue: No ]

Number of Participants With NRTI Associated Mutations at Time of Treatment Failure Through Week 48 and 96 [ Time Frame: Screening, time of failure through Week 48, Week 96 ] [ Designated as safety issue: No ]

Genotypic resistance to NRTIs was assessed by identification of relevant mutations at screening using MBPSGT assay and repeated for all participants with HIV-1 viral load more than 500 copies/mL at treatment failure through week 48 and week 96. Following mutations associated with NRTIs were summarized at time of failure: Any zidovudine/lamivudine (Zid/Lam), Any thymidine analogue-associated mutation (TAM), methionine (M) to valine/isoleucine (V/I) substitution at residue (r) 184 (M184V/I), lysine (K) to arginine (R) substitution at residue 65 (K65R) and any other NRTI mutations.

Number of Participants With Efavirenz Associated Mutations at Time of Treatment Failure Through Week 48 and 96 [ Time Frame: Screening, time of failure through Week 48, Week 96 ] [ Designated as safety issue: No ]

Genotypic resistance: mutations at screening by MBPSGT assay, repeated if viral load >500 copies/mL at treatment failure through week 48, 96. Efavirenz mutation:lysine to aspargine at r103(K103N);tyrosine to cysteine/isoleucine at r181(Y181C/I);tyrosine to cysteine/leucine/histidine at r188(Y188C/L/H);glycine to alanine/serine at r190(G190A/S);valine to alanine to r106(V106A);leucine to isoleucine at r100(L100I);alanine to glycine at r98(A98G);lysine to glutamic acid at r101(K101E);valine to isoleucine at r108(V108I);proline to histidine at r225(P225H);methionine to leucine at r230(M230L).

Association between baseline resistance and virological response was assessed as percentage of participants with HIV-1RNA levels less than 50 copies/mL by OSS at screening. OSS categorized as 0, 1, 2, >3 (maximum value of 6) and calculated as the sum of the net assessment of in-vitro phenotypic and genotypic susceptibility using a binary scoring system (0= resistant, 1= sensitive or susceptible) for each antiretroviral agent in OBT. Higher scores indicate greater susceptibility.

Other Outcome Measures:

Percentage of Participants With Viral Load of Less Than 400 Copies/mL and Less Than 50 Copies/mL of HIV-1 RNA at Week 96 [ Time Frame: Week 96 ] [ Designated as safety issue: No ]

Following a review of the interim analysis data, the DSMB recommended to terminate the UK-427,857 300 mg QD arm based on pre-specified protocol non-inferiority criteria not being met for the QD arm versus efavirenz

Genotypic or phenotypic resistance to efavirenz, zidovudine or lamivudine

X4- or dual/mixed-tropic virus or repeated assay failure

Any other clinical condition that, in the Investigator's judgement, would potentially compromise study compliance or the ability to evaluate safety/efficacy

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Please refer to this study by its ClinicalTrials.gov identifier: NCT00098293